1. Field of Invention
The invention relates to an opto-electrical packaging and, in particular, to an opto-electrical packaging technique that utilizes an alignment mechanism and a molding packaging means to increase the yield and to lower the cost.
2. Related Art
In accord with the high-speed broadband communication trend in the future, the optical communication industry that uses light as the communication medium prospers in recent years. Fiber products for optical communications also become more important. High-speed transmission systems using optic fibers as the media have to have high-quality transceiver module in support in order to satisfy users' needs. The main elements in an optical transceiver module include a light-emitting device, a photo detector, a converging lens, a control circuit board, and fiber connectors. The packaging of the normal optical transceiver modules requires an active alignment method to align the opto-electrical devices in order to have precision alignment between the opto-electrical devices and the converging lens. Currently, such an alignment task is performed manually. This requires more time and manpower, while the yield cannot be easily increased. Therefore, this method is not ideal for mass production. Consequently, how to develop a new packaging technique for optical transceiver modules in such a way that opto-electrical devices are precisely aligned with a higher yield but a lower cost has been an important subject in the optical communication industry.
Traditionally, most optical transceiver modules adopt an edge-emitting laser light-emitting diode (LED) as their light-emitting device. The laser beam is emitted from the edge surface of the chip. In recent years, the development in the vertical cavity surface emitting laser (VCSEL) has greatly increased the functions of the optical transceiver module. In comparison with the edge-emitting laser, the VCSEL has a higher output power, a smaller spreading angle, and a rounder beam output. Besides, the VCSEL can provide wafer-grade tests for individual devices. Therefore, the VCSEL has wider applications and has received great attention in using it as the light source of the optical transceiver module.
The packaging structure of a VCSEL optical transceiver module in the prior art usually uses a metal case, as disclosed in the U.S. Pat. No. 6,031,856. The design of the packaging structure is to install the VCSEL on a substrate. A metal case is used to package the module. The electrical signals are output from the metal pins underneath the package. A converging lens is installed at where light is emitted. Such a design requires active alignments between the chip and the lens. Therefore, the material cost is higher and the packaging size is larger.
To increase the density of the assembled module and to lower the cost, a molding packaging means is developed for integrated circuit (IC) device packaging. For example, the U.S. Pat. No. 5,506,445 uses a leadframe to install the VCSEL and a transparent plastic material to package it. A lens for converging light is formed directly from the plastic material. In the U.S. Pat. No. 5,123,066, however, the leadframe is used for electrical communications. It also uses a plastic material for packaging. After packaging, the pins of the leadframe are connected to an external conductive circuit. Using the molding packaging means can lower the packaging cost and thus becomes the mainstream these days. Nevertheless, the molding packaging means currently used has to extend pins from the leadframe to outside in order to output electrical signals. The packaging size thus increases. Moreover, the current molding packaging means does not provide a precision alignment mechanism for the opto-electrical devices, lenses, and optic fiber connectors. As a result, the yield of opto-electrical packaging cannot be significantly increased.